1. Field of the Invention
The present invention relates to terrestrial Digital Multimedia Broadcasting (DMB), and more particularly to a method for providing an Electronic Program Guide (EPG) schema based on eXtensible Markup Language (XML) in terrestrial DMB.
2. Description of the Related Art
The Digital Multimedia Broadcasting (DMB) is a system standard which the Republic of Korea is trying to build in order to provide a multimedia broadcasting service including video, based on the Digital Audio Broadcasting (DAB; Eureka-147) system. The DAB system is a European digital radio broadcasting standard for providing both a high quality audio service of CD quality and a data service. The DMB includes satellite DMB, which uses satellites as a transmission media, and terrestrial DMB, which uses ground waves as transmission media.
With a DMB system, it is possible to provide not only video information but also various other information types, such as audio and data. Particularly, in the terrestrial DMB, the video, audio, and data services are separately and individually transmitted in a frequency domain referred to as an “Ensemble.”
In the terrestrial DMB, it is important to provide EPG (Electronic Programming Guide) information. To this end, the terrestrial DMB proposes to provide information through an XML scheme.
According to the XML scheme, contents and expression of a document are separately transmitted, so that a document maker can make a document without paying attention to the expression of the document. Further, it is possible to express one XML document in various ways by using various style sheet documents.
The XML document by itself is not aimed at expression of information but is aimed at structural storage of information. Therefore, in order to express an XML document by Hyper Text Markup Language (HTML), it is necessary to prepare separate style sheet documents, such as Cascading Style Sheet (CSS) documents or eXtensible Stylesheet Language (XSL) documents.
FIG. 1 is a block diagram of a typical XML document providing system for providing EPG information in a terrestrial DMB, which includes a document maker 100 for making an XML document, a document receiver 200 for receiving the produced XML document in the form of a web document and then translating the received document, and a broadcasting network 14 for interconnecting the document maker 100 and the document receiver 200.
Specifically, the document maker 100 converts an input document 11 to an XML document by using an XML maker 12 and then transfers the XML document to the broadcasting network 14. In order to convert the XML document expressed by only the contents thereof into an HTML document, etc., the document maker 100 further includes a Cascading Style Sheet/eXtensible Stylesheet Language (CSS/XSL) unit 13 which provides style sheet documents.
Further, the document receiver 200 receives the XML document from the broadcasting network 14 and translates the XML document by using an XML translator 15, thereby converting the document into an HTML type document 16.
In order to generate XML-based EPG information for such a terrestrial DMB, the European Telecommunications Standards Institute (ETSI) has built an XML-based EPG standard (ETSI TS 101 818) for Digital Audio Broadcasting (DAB) which proposes an XML schema for data broadcasting.
In general, the EPG information reports information about various services provided to broadcast service users, so that the users can select a broadcast service or related contents which the users want.
The EPG information needs to be flexible as various different terminals are used in the broadcasting network. Therefore, in order to provide EPG information regardless of the different terminal types, the ETSI has defined an XML schema for DAB service using XML.
As described above, the EPG defined by the ETSI is based on the DAB service, and the Telecommunications Technology Association (TTA) of the Republic of Korea is currently doing additional work for the part for the terrestrial DMB service, that is, for the video service-related part.
The XML schema defined in the “ETSI TS 101 818” according to the DAB standard includes service information, schedule information, and group information.
Table 1 shows an example of a schema for the service information from among the XML schemas as described above.
TABLE 1<xs:element name=“service” minOccurs=“0” maxOccurs=“unbounded”><xs:complexType><xs:sequence><xs:element name=“serviceID” minOccurs=“1”maxOccurs=“unbounded”><xs:complexType><xs:attribute name=“id” type=“epg:dabIDType” use=“required”/><xs:attribute name=“type” default=“primary”><xs:simpleType><xs:restriction base=“xs:NMTOKEN”><xs:enumeration value=“primary”/><xs:enumeration value=“secondary”/></xs:restriction></xs:simpleType></xs:attribute></xs:complexType></xs:element><xs:group ref=“epg:serviceNameGroup” maxOccurs=“unbounded”/><xs:element  name=“mediaDescription”  type=“epg:mediaDescriptionType”minOccurs=“0” maxOccurs=“unbounded”/><xs:element  name=“genre”  type=“epg:genreType”  minOccurs=“0”maxOccurs=“unbounded”/>minOccurs=“0” maxOccurs=“unbounded”/><xs:element  name=“parentalRating”  type=“epg:parentalRatingType”minOccurs=“0”/><xs:element name=“CA” type=“epg:CAType” minOccurs=“0”/><xs:element name=“keywords” type=“epg:keywordsType”minOccurs=“0”/><xs:element  name=“link”  type=“epg:linkType”  minOccurs=“0”maxOccurs=“unbounded”/></xs:sequence><xs:attribute name=“version” type=“xs:integer”/><xs:attribute name=“format” default=“audio”><xs:simpleType><xs:restriction base=“xs:NMTOKEN”><xs:enumeration value=“audio”/><xs:enumeration value=“DLS”/><xs:enumeration value=“MOTSlideshow”/><xs:enumeration value=“MOTBWS”/><xs:enumeration value=“TPEG”/><xs:enumeration value=“DGPS”/><xs:enumeration value=“proprietary”/></xs:restriction></xs:simpleType></xs:attribute><xs:attribute name=“bitrate” type=“xs:nonNegativeInteger”/></xs:complexType></xs:element></xs:sequence><xs:attribute name=“id” type=“epg:ensembleIDType” use=“required”/><xs:attribute name=“version” type=“xs:integer”/></xs:complexType></xs:element>
In general, the terrestrial DMB service is provided through ensembles, each of which contains information about a specific service. According to the XML structure, an element named “service information” includes a lower layer element named “ensemble,” and the element “ensemble” includes a lower layer element named “service.” Further, one of the attributes of the element “service” is “format.” According to the definition in the DAB standard, “format” may possess one of seven attributes selected from “audio(default),” “Dynamic Layer Service (DLS),” “MOTSlideshow,” “MOTBWS,” “Transport Protocol Experts Group (TPEG),” “Differential GPS (DGPS),” and “proprietary.”
According to the conventional method for providing the EPG information, only one of the seven attributes (audio, DLS, MOTSlideshow, MOTBWS, TPEG, aDGPS, and proprietary) can be selected and set as the attribute of the element “format,” as shown in Table 1.
The conventional “service” element defined by the “ETSI 101 818” employs an attribute value named “format” to express the property of the service. However, such an attribute value is only one of “audio”, “DLS”, “MOTSlideshow”, “MOTBWS”, “TPEG”, “DGPS”, and “proprietary.”
When the “format” is “audio,” it implies that the corresponding service provides audio. Or, when the “format” is “DLS,” it implies that the corresponding service is an audio providing service which provides DLS along with the audio.
However, according to the conventional EPG schema as described above, the “format” is defined as an attribute and is thus allowed to have only a single value. Therefore, when there are two or more data services related to the audio service, it is impossible to express the data services. However, the terrestrial DMB service can simultaneously provide a service for audio and video combined data. For example, while a user is listening to a song (audio), words of the song may be simultaneously displayed on a screen by using the DLS. Or, while a user is viewing a video, the user may navigate web sites in relation to the video program by using a BWS browser or a downloaded application program.
Hence, the current terrestrial DMB provides various types of services, which may go beyond the range of expression defined in the existing EPG schema.